Technical Field
The present disclosure relates to a light emitting device.
Description of the Related Art
Light emitting devices that use light emitting elements, called light emitting diodes (hereinafter, also referred to as “LEDs”), have been gaining attention. Various types of light emitting devices that use LEDs and that emit white light have been known. An example thereof is a light emitting device formed from a combination of an LED emitting blue light and a phosphor emitting yellow light. This is a light emitting device emitting white light by mixing the colors of the blue light of the blue LED and the yellow light of the phosphor that has been excited by the blue light.
With the light emitting device formed from a combination of the light emitting element emitting the blue light and the phosphor emitting the yellow light, although high radiant intensity in the visible light region and high luminous efficacy are achieved, radiant intensity in the blue-green region and in the red region may not be sufficiently achieved. Because of this, there is room for further improvement in the color rendering index average, which is an index of color appearance of an irradiated object (color rendering index).
The evaluation procedure of the color rendering index of a light source is stipulated by JIS Z 8726 and is performed by calculating the numerical value of the difference in color ΔEi (i is an integer of 1 to 15) for cases where a test color having a particular reflectance characteristics (R1 to R15) is measured using each of test light source or reference light source. Note that the upper limit of the color rendering index Ri (i is an integer of 1 to 15) is 100. That is, a smaller difference in color between the test light source and the reference light source having a color temperature corresponding thereto results in a higher color rendering index that is closer to 100.
Regarding the description above, light emitting devices that use an LED emitting blue light and two types of phosphors emitting yellow to green light have been proposed and are said to be able to achieve excellent color reproducibility (e.g. see JP 2003-535477 A and JP 2003-535478 A).